A breatharian is a person who does not eat or drink and is nourished by pure energy. Some sources say that breatharians live of light, some say they live of prana, others say it is sunlight, or air. Trying to figure out what nourishes a breatharian, I found two categories in all of this.
For a closer description and comparison on each of these sources of nourishment, see this page.

Living on light
One of the two types of breatharians I found, are those who live on light.

Light: Light is the complete matter from which all matter originates and exists within. Light contains all colors, colors are the smallest auric aspects of any type of matter or atom, these in turn are everything that exists including nutrition and our body.Requirement 1: For a person to live on light, there are a number or requirements. When a person is in denial of an aspect of themselves, their energy flow is blocked. Denial creates these blockages. A person who knows who they are, and accepts who they are, has no blockages or denials and gets an active energy flow (very rare). The person's aura becomes white. The white light is now flowing in the body. Being all of who one is, is a requirement.Requirement 2: Consciousness of who one is makes the DNA active and magnetic. And so, when any part of the body, eg. blood cells or hair, needs to be built, and there is the need of body material, the DNA pulls from the light that now flows in the body, the colors which will manifest the required body material. There is instant manifestation of the body.The breatharian: This kind of breatharian lives of life alone. The person does not eat, does not drink. There is never any hunger or thirst. Sleep is for only a few hours at night. This breatharian has never ending energy. Ageing is stopped and reversed. A breatharian with active DNA is immortal.

Living on Prana/Sunlight/AirThe second category of breatharians are the ones who do not live of light, but do not eat or drink. They live of other forms of energy.

Prana/Sunlight/Air: Whereas white light contains the source of all colors and wavelengths, which simply are other aspects of a type of material, prana, sunlight and air do not. White light is the strongest, purest and only complete energy.Prana: Prana is an etheric substance, yellow white in color. It is a specific form of liquid energy which supports biological life. A person does not require an active energy flow or active DNA to live of prana. Eating food tends to block the effects of prana. Not eating makes the effects of prana stronger, this is because the little amount of prana we can find is often too 'quiet' comparing to the 'loud dense' energies of the foods we eat. We only require a small amount of dense food material for the 'voice' or 'wavelength' of prana to be too weak to have effect.Sunlight: Sunlight contains various wavelengths which manifest their corresponding body material when they reach the body. Sunlight does not contain all wavelengths, and thus can not provide with all nutrients.Air: This is a more chemical source of nutrition. Nitrogen for example combines with other already existing substances to form other nutrients.Requirements: Prana requires first of all that the person eats less of the dense harmful foods. The toxins in our food destroy not only antioxidants and cells but also prana. And secondly, the inadequate amounts of prana in many areas of the world require that the person spends a few minutes every day consciously breathing in and accumulating prana into their body for prana to be a sufficient source of nutrition. As for living on sunlight, it may require a warmer climate, especially since warmth itself is a wavelength from the sun and there is less of it in winters. Living on air requires an excellent breathing technique, deep breathing. It can be difficult to learn, but is very effective. But air does not contain even close to many of the vital nutrients our body needs to function. And our air can not provide us with antioxidants, nutrients that guard our body from the harm of polluted air. People have added toxins to the air, but forgotten to add the neutralising antioxidants! ;)The disadvantages: Living on prana alone provides with up to 80% of required nutrients, but does not give immortality or necessarily stop ageing. Sunlight is inadequate as a single source of nourishment. Sunlight combined with air, too, are not sufficient. Air alone won't work. Especially the skeleton will suffer if a person tries to live of air alone.The breatharian: Skills are required to live on any combination of prana/sunlight/air. Such as meditating to accumulate prana, being out in the sun, and deep breathing. Nor is it completely 100% effective and the person may need to drink or eat a little now and then. I recommend that a person living on these is cautious. The wanting to 'stop eating' should, I think, not be top priority. Your health and well being should be what you find most valuable.

Three types of breatharians
Although I'd say there are two types of breatharianism that works, there are perhaps three ways, of which I am sceptic toward this third one.

People who are not in tune to prana or light may still try to find breatharianism, this by relying on living on sunlight and air. Sunlight and air are some of the things we can easily perceive of this world, they are dense enough. But if we try to live without the less dense nutrition - such as found in prana or light - our less dense aspects die off and we can't live without these. It may work to stay alive for a period of time, although it does not provide with enough wavelengths to keep the entire human body completely well, thriving or immortal. My guess is that a person can survive on sunlight and air, but will keep ageing and suffer from nutrient deficiencies.

This page is all according to my thoughts and conclusions. Based mainly on tuning in, in other words an intuition which doesn't seem to fail. It could also be proven in science, but that work is extensive and I'll deal with that part later in life.